Using an include macro can generate weird empty paragraphs

The following xwiki/2.1 syntax code:

{{include reference="DoesNotMatterIfExistsOrNot"/}}{{velocity}}
hi
(((ho)))
{{/velocity}}

generates the following html output:

<p></p>      <--- why?
<p>hi</p>
<div><p>ho</p></div>
<p></p>      <--- why?

The problem seems to occur when the include macro is used next to the velocity macro (possibly other inline macros that support wiki syntax?) and inside that macro, a group is defined.

Those empty paragraphs generated before and after the include-velocity macro pair can cause HTML validation problems

Note: when the included document does exist and contain content, the output is this:

<p></p>          <--- why?
<p>aa</p>        <--- content of the included document
<p>hi</p>
<div><p>ho</p></div>
<p></p>          <--- why?

Workaround for getting rid of the paragraphs:

((({{include reference="DoesNotMatterIfExistsOrNot"/}}{{velocity}}
hi
(((ho)))
{{/velocity}})))

obviously outputs:

<div>
  <p>hi</p>
  <div><p>ho</p></div>
</div>